2
的startUpload方法內<Items />將調用回調函數來更新在每次接收到的響應時間的父組件的狀態，這將導致<Items />不必要地多次渲染。如何避免重複渲染反應組件？
我預期的效果是，狀態更新後，只有<Results />組件需要重新呈現
class Parent extends React.Component {
constructor(props) {
super(props);
this.getResponseData = this.getResponseData.bind(this);
this.state = {
responseData: [],
}
}
getResponseData(data) {
this.setState({
responseData: this.state.responseData.concat(data),
})
}
render() {
return (
<div>
<Items files={this.props.files} updateData={this.getResponseData}/>
<Results data={this.state.responseData}/>
</div>
)
}
}
class Items extends React.Component {
componentDidMount() {
this.startUpload(this.props.files)
}
startUpload(files) {
const URL = 'http://localhost:3000/upload';
for (let i = 0, len = files.length; i < len; i++) {
const data = new FormData();
data.append('img', files[i]);
fetch(URL, {
method: 'post',
body: data,
})
.then(checkStatus)
.then(parseJSON)
.then(data => {
this.props.updateData(data);
})
}
}
render() {
const filesData = this.getFilesData(this.props.files);
let imageItems = filesData.map((current) => {
return (
<div>
<img src={current.objectURL} alt="preview"/>
</div>
)
});
return <div>{imageItems}</div>;
}
}
function Results(props) {
const responseData = props.data;
let result = [];
if (responseData.length) {
result = responseData.map(current => {
return <p>{current}</p>
});
return <div>{result}</div>
}
}
查看'React'方法：「shouldComponentUpdate」。 [LifeCycle]（https://facebook.github.io/react/docs/react-component.html） – Tikkes
@Tikkes這個API可以解決我的問題，謝謝 – isbase